A plurality of indexable inserts for turning, reaming, planing, milling, boring and the like are known in machining technology that are designed in a work tool to effect a highest possible cutting capacity with an advantageous formation of the chips and whose distance from the cutting area is the same. The target value of these indexable inserts, as mentioned above, is definitely the cutting capacity, whereby the accumulating, essentially coarse chips are broken and/or prepared, where applicable, by means of deformation by chip-breaking tools of the cutting plates for quick, targeted discard.
In reaming, undersized pre-drilled holes are slightly expanded to a high-precision dimension, in order to achieve and ensure a dimensionally accurate transition of components.
Reamers are tools for fine finishing borehole surfaces, whereby the drilled surfaces may be designed as blank holes or as throughholes, and they are mostly formed by a traction part and a tool part with at least one cutting tip. The cutting tips have at least one main cutting edge, which may be formed from several components, and at least one auxiliary cutting edge.
Naturally, with the fine finishing of surfaces, in particular with the reaming of boreholes, substantially different conditions concerning an insertable cutting plate shape as well as chip formation advantageously prevail in comparison with a performance-oriented chip removal from work pieces, but the type as well as the shape and flow of the fine chips removed also greatly influence the quality of borehole surfaces attainable and the service life of the tool in reaming.
According to the state of the art, reamers are provided with differently oriented main and auxiliary cutting edges.
For example, from patent EP 1 160 042, a chip breaker is known that constantly limits the chip-bearing surface facing the cutting edges in the area of the main cutting edge and the auxiliary cutting edge, whereby the chip breaker rises in the area of the main cutting edge and has a decreasing distance to the main cutting edge. Normally, the main cutting edge is used for the roughing operation and the auxiliary cutting edge is used for fine finishing and the chips removed from the cutting edges hit a preferably straight chip breaker and are broken, receiving as well a velocity impulse in a direction that is determined by the slope of the chip breaker.
EP 0 631 834 B1 disposes a cutting tip for a reamer for the fine finishing of metallic work pieces with a main cutting edge and an auxiliary cutting edge as well as a chip-bearing surface protruding toward these cutting edges and with a chip breaker limiting the latter. In order to achieve short chips in fine finishing, the chip breaker is provided with a high point at the vertex of the cutting edges, from which the chip breaker slopes in the area of the main cutting edge and, in the area of the auxiliary cutting edge, it is designed parallel to the latter, or it may likewise be sloping.
However, all cutting plates for reamers according to the state of the art have the same disadvantage in that the flat chip bearing surfaces of the main cutting edge and the auxiliary cutting edge are facing the cutting edges, which collect the chips in particular in the area of the auxiliary cutting edge, whereby, due to the clogging of chips, increased chip removal may result in higher friction coefficient factors and in the generation of heat as well as a reduced surface quality during the fine finishing of the work piece.